local f = string.format

-- if allow_unregistered is false or absent, if the original item or its alias is not a registered item, will return nil
function futil.resolve_item(item_or_string, allow_unregistered)
	local item_stack = ItemStack(item_or_string)
	local name = item_stack:get_name()

	local seen = { [name] = true }

	local alias = minetest.registered_aliases[name]
	while alias do
		name = alias
		seen[name] = true
		alias = minetest.registered_aliases[name]
		if seen[alias] then
			error(f("alias cycle on %s", name))
		end
	end

	if minetest.registered_items[name] or allow_unregistered then
		item_stack:set_name(name)
		return item_stack:to_string()
	end
end

function futil.resolve_itemstack(item_or_string)
	return ItemStack(futil.resolve_item(item_or_string, true))
end

if ItemStack().equals then
	-- https://github.com/minetest/minetest/pull/12771
	function futil.items_equals(item1, item2)
		item1 = type(item1) == "userdata" and item1 or ItemStack(item1)
		item2 = type(item2) == "userdata" and item2 or ItemStack(item2)

		return item1 == item2
	end
else
	local equals = futil.equals

	function futil.items_equals(item1, item2)
		item1 = type(item1) == "userdata" and item1 or ItemStack(item1)
		item2 = type(item2) == "userdata" and item2 or ItemStack(item2)

		return equals(item1:to_table(), item2:to_table())
	end
end

-- TODO: probably this should have a 3nd argument to handle tool and tool_group stuff
function futil.get_primary_drop(stack, filter)
	stack = ItemStack(stack)

	local name = stack:get_name()
	local meta = stack:get_meta()
	local palette_index = tonumber(meta:get_int("palette_index"))
	local def = stack:get_definition()

	if palette_index then
		-- https://github.com/mt-mods/unifieddyes/blob/36c8bb5f5b8a0485225d2547c8978291ff710291/api.lua#L70-L90
		local del_color

		if def.paramtype2 == "color" and palette_index == 240 and def.palette == "unifieddyes_palette_extended.png" then
			del_color = true
		elseif
			def.paramtype2 == "colorwallmounted"
			and palette_index == 0
			and def.palette == "unifieddyes_palette_colorwallmounted.png"
		then
			del_color = true
		elseif
			def.paramtype2 == "colorfacedir"
			and palette_index == 0
			and string.find(def.palette, "unifieddyes_palette_")
		then
			del_color = true
		end

		if del_color then
			meta:set_string("palette_index", "")
			palette_index = nil
		end
	end

	local drop = def.drop

	if drop == nil then
		stack:set_count(1)
		return stack
	elseif drop == "" then
		return nil
	elseif type(drop) == "string" then
		drop = ItemStack(drop)
		drop:set_count(1)
		return drop
	elseif type(drop) == "table" then
		local most_common_item
		local inherit_color = false
		local rarity = math.huge

		if not drop.items then
			error(f("unexpected drop table for %s: %s", stack:to_string(), dump(drop)))
		end

		for _, items in ipairs(drop.items) do
			if (items.rarity or 1) < rarity then
				for item in ipairs(items.items) do
					if (not filter) or filter(item) then
						most_common_item = item
						inherit_color = items.inherit_color or false
						rarity = items.rarity
						break
					end
				end
			end
		end

		if not most_common_item then
			return
		end

		most_common_item = ItemStack(most_common_item)
		most_common_item:set_count(1)

		if inherit_color and palette_index then
			local meta2 = most_common_item:get_meta()
			meta2:set_int("palette_index", palette_index)
		end

		return most_common_item
	else
		error(f("invalid drop of %s? %q", dump(name, drop)))
	end
end